Nature Loves Newton!! If not she wouldn’t give such an importance for the scientist’s words. “every action has an equal and opposite reaction”. Global Dimming is also a phenomenon, basically admired from those words. Lets see how..
Heat budget of the earth:
Two weeks back our Finance minister came parliament carrying a Black suitcase having some big number of papers. That suitcase had the Budget of the nation, according which the country is about to run. For our purpose, put it like this BUDGET = INCOMING MONEY- OUTFLOWING MONEY.
If you get 0 as the answer, then we may assume that the economy is stable. Like a nation, even the earth also frames a budget, due to which it sustains, since the BIG-BANG. Unlike our nation, earth’s budget provides a wise balance between every component, until the human intervene. Earths heat budget = incoming radiation – outgoing radiation (reflected heat). Till 1800, incoming heat = out-flowing heat (more or less). But the industrial revolution after 1800 introduced a new concept called global warming.
Earth’s Heat Budget:
It is an average rise in earth’s mean annual temperature. Warming of the climate system primarily caused by increasing concentrations of greenhouse gases produced by human activities such as burning of fossil fuels and deforestation. The greenhouse effect is the process by which absorption and emission of infrared radiation by greenhouse gases in the atmosphere warm a planet’s lower atmosphere and surface i.e these gases do not allow the outflowing heat, thus making warmer. Now a byproduct of the global warming is called as global dimming.
Fossil fuels when used, creates other by-products. These by-products are pollutants, such as sulphur dioxide, soot and ash. These pollutants can change the properties of clouds. Clouds are formed when water droplets are seeded by air-borne particles, such as pollen, dust (which acts as the nuclei/platform to hold moisture). Polluted air results in clouds with larger number of droplets than unpolluted clouds. This then makes those clouds more reflective. Aerosols which form from pollution can directly reflect and absorb radiation before it reaches the planet’s surface and make clouds brighter and longer lasting, meaning they reflect more sunlight. More of the sun’s heat and energy is therefore reflected back into space. This reduction of heat reaching the earth is known as Global Dimming.
- At first, it sounds like an ironic savior to global warming. But in near future this may be fatal enemy than global warming. Scientists say, that the impact of global dimming might not be in the millions, but billions. The Asian monsoons bring rainfall to half the world’s population. If this air pollution and global dimming will keep on increasing, it will have its adverse impact on the Asian monsoons and some 3 billion people could be affected.
- Only if ocean gets warm, it will have the tendency to initiate the rain formation. Global dimming might have caused the droughts in Ethiopia in the 1970s and 80s where millions died, because the northern hemisphere oceans were not warm enough to allow rain formation. Also particulate pollution might have changed the properties of clouds—so-called “brown clouds” are more reflective and produce less rainfall than their more pristine counterparts.
- The pollutants that lead to global dimming also lead to various human and environmental problems, such as smog, respiratory problems, and acid rain.
- Vegetation will die off even more quickly.
- Soil erosion will increase and food production will reduce.
- A Sahara type of climate could be possible in places such as England, while other parts of the world would fare even worse.
- Such an increase in temperature would also release one of the biggest stores of greenhouse gases on earth, methane hydrate, currently contained at the bottom of the earth’s oceans and known to destabilize with warming. This gas is eight times stronger than carbon dioxide in its greenhouse effect. Due to the sheer amounts that would be released, by this time, whatever we would try to curb emissions, it would be too late.
If the problem is not promptly addressed could lead to an increase of 10 degrees centigrade in temperature over the next 100 years, not the standard 5 degrees which most models currently predict.
Global dimming can be dealt by cleaning up emissions. While the southern hemisphere saw modest dimming in the period 1961–90 (which has continued till date), the northern hemisphere saw much more significant dimming effect. Since then some parts of the world, such as Europe and North America, have seen partial recovery due to various emission cut strategies (known as “brightening”), while other regions (most notably China and India) have seen steep rise in dimming effect due to rapid industrialization.
However, if global dimming problems are only addressed (without concerning about global warming), then the effects of global warming will increase even more. This may be what happened to Europe in 2003. In Europe, various measures have been taken in recent years to clean up the emissions to reduce pollutants that create smog and other problems, but without reducing the greenhouse gas emissions in parallel. This seems to have had a few effects:
- This may have already lessened the severity of droughts and failed rains in the Sahel.
- However, it seems that it may have caused, or contributed to the European heat wave in 2003 that killed thousands in France, saw forest fires in Portugal, and caused many other problems throughout the continent.
It should be noted that the impacts of addressing global dimming only would increase global warming more rapidly and brings Irreversible damage in Global level (in next 20 years) which would include:
- The melting of ice in Greenland, which would lead to more rising sea levels. This in turn would impact many of our major world cities.
- Drying tropical rain forests would increase the risk of burning. This would release even more carbon dioxide into the atmosphere, further increasing global warming effects.
The only way to control this villain, is as Climatologists are stressing that the roots of both global dimming causing pollutants and global warming causing greenhouse gases have to be dealt with together.